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Subject[PATCH net 2/4] mptcp: fix scheduling with atomic in timestamp sockopt
From: Gang Yan <yangang@kylinos.cn>

Using lock_sock_fast() (atomic context) around sock_set_timestamp()
and sock_set_timestamping() is unsafe, as both helpers can sleep.

Replace lock_sock_fast() with sleepable lock_sock()/release_sock()
to avoid scheduling while atomic panic.

Fixes: 9061f24bf82e ("mptcp: sockopt: propagate timestamp request to subflows")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260420093343.16443-1-gang.yan@linux.dev
Signed-off-by: Gang Yan <yangang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
net/mptcp/sockopt.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 79db15903e7a..0efe40be2fde 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -159,10 +159,10 @@ static int mptcp_setsockopt_sol_socket_tstamp(struct mptcp_sock *msk, int optnam
lock_sock(sk);
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
- bool slow = lock_sock_fast(ssk);

+ lock_sock(ssk);
sock_set_timestamp(ssk, optname, !!val);
- unlock_sock_fast(ssk, slow);
+ release_sock(ssk);
}

release_sock(sk);
@@ -235,10 +235,10 @@ static int mptcp_setsockopt_sol_socket_timestamping(struct mptcp_sock *msk,

mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
- bool slow = lock_sock_fast(ssk);

+ lock_sock(ssk);
sock_set_timestamping(ssk, optname, timestamping);
- unlock_sock_fast(ssk, slow);
+ release_sock(ssk);
}

release_sock(sk);
--
2.53.0


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